<p>
  The expiration date for an options contract is the time when the contract is no longer valid.
  The expiration date for listed stock options in the United States is usually the third Friday of the contract month, which is the month when the contract expires.
  When that Friday falls on a holiday, the expiration date is on Thursday immediately before the third Friday.
  The options expiration week is a week before options expiration.
</P>
<p>
  During option-expiration weeks, a reduction occurs in option open interest as the near-term options approach their expiration and then expire.
  According to a research from Chris and Licheng <a href="https://www.sciencedirect.com/science/article/pii/S0378426613003051">Returns and option activity over the option-expiration week for S&P 100 stocks</a>,
  Large-cap stocks with actively traded options tend to have higher average weekly returns during option-expiration weeks. In this algorithm, we'll use the real market data to explore the option expiration week effect.
</p>
